The invention relates to an alpine ski boot provided with a sole which permits flexing of the foot during walking.
The first ski boots, being made of leather, were relatively flexible. They offered good comfort and permitted an easy stride, thanks to the flexibility of their sole. In order to assure a good transmission of force between the foot and the ski, that is to say, to reduce the capacity for deformation of the boot, the sole and the upper have become more and more rigid. Consequently, walking has become less and less natural. With the appearance of boots made of plastic materials, the upper, and more particularly the sole has acquired a rigidity assuring an excellent interface between the foot and the ski through the intermediary of a ski binding. This has, however, rendered a normal stride difficult because of the total lack of total flexibility of the sole at the level of the metatarsalphalangeal articulation.
For a certain number of years, various means were used in an attempt to facilitate walking when using plastic alpine boots. Patent EP 0 664 969 foresees a flexible zone forming a hinge or junction point in the rigid metatarsalphalangeal zone of the sole and the use of a boot shell having two articulating portions providing the joint, the two parts being, among other things, connected to a locking device which blocks articulation.
A boot constructed according to the same principal is shown in U.S. Pat. No. 5,572,806. This boot differs from the prior boot in that the locking device is slidingly mounted within the confines of the sole. Such boots do not provide a true flexibility which permits a natural operation of the foot during walking. In addition, in that it has an effect on walking, the boots of the prior art are heavy and of little comfort. Another approach to the problem, putting aside stop-gap measures such as the solutions mentioned above, is described in French patent no. 2130644. It consists of a sort of auxiliary housing in which one encloses a boot to the upper and flexible sole.
It is true that boots intended for the practice of cross-country skiing provide a flexibility at the level of the metatarsalphalangeal zone in such a manner which permits an operation of the foot with a minimum of resistance. Such boots are however fixed only at the front end in the manner that it is not necessary that the sole has a longitudinal rigidity as is the case with the soles of ski boots in the conventional ski binding equipped with a toe piece and heel piece.
Today, the persons practicing leisure skiing would like to find a light and comfortable boot on the market permitting at the same time an easy stride and a ski technique with favorable characteristics where the boot is fixed to a ski by means of a conventional binding.
The invention has the purpose of introducing an alpine ski boot which satisfies this need.
The alpine ski boot according to the present invention is characterized in that it is constituted essentially of an flexible upper; an intermediate sole providing rigid extremities extending beyond the upper at the front and at the rear and further enabling holding elements of a standard ski binding to hold it in the front and the rear; and a flexible sole.
The intermediate sole, preferably of plastic, assures both the flexibility of the sole permitting a natural operation of the foot during walking and the axial rigidity necessary for an alpine ski boot.
According to a first embodiment, the intermediate sole has a flexible intermediate zone.
According to a second embodiment, the intermediate sole is semi-rigid, but has a transverse joint in the metatarsalphalangeal zone. This joint can be formed by a flexible zone of plastic material of which the intermediate sole is constituted.
According to another embodiment, the intermediate sole is made of two rigid parts and the joint is formed by an axle connected to the two rigid parts. This joint is able to provide a stop limiting the rotation in the opposite direction to the rotation associated with the flexure of the foot. According to one embodiment, the boot is equipped with a means of locking the joint, the locking means possibly being controllable by a lever mounted at the rear of the boot.
It is preferred that the standard rigid zones at the extremities are not covered or overlapped by the flexible sole.
Making a turn necessitates a firm lateral support of the heal in the boot. To this end, the intermediate sole should advantageously provide, in the rear, a reinforcement of the heel surrounding the lower posterior region of the upper.
Certain bindings provide a jaw consisting of two arms which push against the upper. In this case, according to one embodiment, the intermediate sole additionally provides a frontal wall which is substantially vertical, contacting the rounded extremity of the upper and intended to receive the support of a fixation jaw. According to a preferred mode of execution of the invention, the flexible sole laterally straddles the intermediate sole and is connected to the upper on the sides. The attached drawings represent, by way of examples, some embodiments of the invention.